Four of the predators are loosed upon the large and polluting shorebird population at the San Juan Capistrano landfill.

Four falcons -- put on the county payroll as part of a five-month experiment to rid a San Juan Capistrano landfill of thousands of gulls -- moved in Tuesday and quickly showed who's boss, harassing and bullying the longtime residents.

As soon as one of the trained falcons was released, the California gulls, considered a menace by employees and a potential source of bacterial pollution by county officials, took to the air.

"While he's in the air, the gulls don't feel comfortable on the ground," said David Knudson, owner of KlearView Resources, the Spokane, Wash., company that supplies the falcons.

The lanner and saker falcons, Knudson said, should quickly establish aerial domination, and the gulls will just as quickly develop a healthy fear of the county dump.

Using falcons to scare off lesser birds is not new. Knudson's falcons have been employed at landfills and military bases throughout the West.

And the mission is always the same: clear the airspace.

"They'll have to go back to what they naturally do for food, which is not eat at a dump," said Knudson of his target. "They now have to learn to live and forage someplace else."

Which is just what the county's Integrated Waste Management Department, which operates the landfill, wants.

The gulls, along with a sprinkling of crows, pigeons, starlings and other scavengers, have dined at the landfill since it opened in 1976.

Feasting on the 2,300 or so tons of municipal waste dumped there daily, the gulls wreak havoc on vehicles and employees, making things, well, messy.

The landfill is three miles from the sea and near the ocean-bound San Juan Creek. The thousands of gulls and other birds that leave their droppings throughout the 1,530-acre landfill create potential health, safety and water-quality hazards.

Over the years, the county has tried many scare tactics to chase away the gulls, including:

A zone gun, which resembles a small cannon that creates a noise at preset intervals. The birds got used to it and ignored it.

Bird wire, strung above the working area on poles in a crisscross fashion. The birds figured out that they could walk under it.

Flash tape, a reflective material that hangs from the wire to scare them. Again, they ignored it and walked under it to get to the garbage.

Bird distress calls, broadcast from an earthmover equipped with a loudspeaker. The birds adapted and ignored it.

Kaleidoscope lights, like a disco. That lasted about half a day before it became clear they wouldn't do the trick.

Inflatable owls placed around the site. The birds got used to them.

Whistles and noisemakers. They got used to them.

Cracker shells, very loud explosions from a shotgun. Nearby residents complained about the noise, and the department discontinued their use.

With few options left, county officials turned to Knudson, who has rid other landfills of problem birds. The falconer, who has 18 birds, some as hunting partners and others specifically trained for bird control, has contracts with about six landfills and military bases in the West.

The falcons do not necessarily harm the gulls, unless the birds unwisely choose to ignore the raptors.